Understanding working of nuclear reactor and japanes accident





Nuclear Reactor
It is powerful device, wherein the nuclear energy produced is utlisied for constructive purposes. A nuclear reactor is based upon controlled nuclear chain reaction.
Construction : The main components of nuclear reactor are follows :

(1) Nuclear Fuel : It is a fissionable material to be used for the fission process to take place. Commonly used fuels in a nuclear reactor are U233, U235 , Pu239 etc. Generally, pure 92U235 is taken inside the sealed aluminium cylinders piled in fission chamber. When slow neutron interact with the fuel, the fission starts and the energy is released.
(2) Moderator : its function is to slow down the fast moving secondary neutrons produced during the fission. The material of moderator should be light and it should not absorb neutrons. Usually, heavy water, graphite, deuterium and paraffin etc. can act as moderators. These moder`tors are rich in protons.
When fast moving neutrons collide head on with the protons of moderator substances, their energies are interchanged sand thus the neutrons are slowed down. Such neutrons are called thermal neutrons which cause fission of U235 in the fuel.
(3) Control rods : They have the ability to capture the slow neutrons. To control the chain reaction from becoming violent, rods of boron or cadmium (called control rods) are inserted in the holes of reactor core, up to a desirable length. As a result of it, the desired number of neutrons absorbed and only limited number of neutrons are left to produce fission. These rods can be adjusted from outside the reactor, in order to control the chain reaction.
In addition to control rods, reactors are provided with safety rods, which when required, can be inserted into the reactor. They reduce the neutron reproduction factor (K) to less than unity.
(4) Coolant : A substance which is used to remove the heat produced and transfer it from the core of the nuclear reactor to the surroundings is called coolant. At ordinary temperatures, water and heavy water serve as coolants but at high temperatures, generally liquid sodium is used as a coolant.
The coolant takes up the heat energy produced in nuclear fission and passes on this energy to water in a heat exchanger. As a result of it, superheated steam is produced which drives a turbine coupled with an electric generator, (5) Shielding : The whole reactor is protected with concrete walls, 2 to 2.5 meters thick, so that radiations emitted during nuclear reactions may not produce harmful effects on the persons working on the reactor.
Working : Fig. outline the working of nuclear reactor. Slow neutrons cause the fission of U235 nuclei. FP stands for fission product. To start the nuclear reaction, the cadmium rods are slowly removed and to stop it, they are inserted. This brings out a controlled nuclear chain reaction and hence the energy produced can be used for constructive purposes.
The nuclear reactors working in India are Apsara, Zerlina, CIR (Canada India Reactor) and Dhruva.
Uses :
(I) Nuclear reactors are used to produce radioactive isotopes which in turn are used in medicine, industry and agriculture.
(II) They are used in electric power generation.
(III) They can be used for the propulsion of ships, submarines and air crafts.
(IV) They are used to produce neutron beam of high intensity which is used in the treatment of cancer and nuclear research.

Japanese Accident


What had happen in japan is that due to sudden tsunami waves the electricity immediately get off due to which cooling system get immediately tipped off but the energy which was generating inside keep on producing heat.Due to which the pressure of radioactive gas keeps on increasing.Above a certain pressure explosion takes place due to which gases get released in atmosphere.Radioactive iodine cause thyroid cancer.To protect it Japanese government has distributed Potassium iodide tablet .Moreover radioactive iodine is having half life of only eight days(the time it takes to become half of the initial value)So most it gone in two months
But radioactive forms of particular cesium persist much longer and in the regions of Chernobyl,They are the still main threats to human health and will be for decades

Comments

  1. thnkzz fr providing wid d information. PLease also tell how to avoid/precautions to avoid these kinds of accident.

    ReplyDelete

Post a Comment

Popular posts from this blog

Energy stored in stretched string

How physics define cooling and natural way of cooling

PHYSICS PROBLEM ON ONE DIMENSIONAL MOTION